1. Field of the Invention
The present invention relates to a method of manufacturing a silicon carbide substrate and more particularly to a method of manufacturing a silicon carbide substrate capable of suppressing variation in plane orientation in a main surface.
2. Description of the Background Art
In recent years, in order to achieve a higher breakdown voltage and lower loss of a semiconductor device, use thereof in an environment at high temperature and the like, silicon carbide has increasingly been adopted as a material for forming a semiconductor device. Silicon carbide is a wide band-gap semiconductor greater in band gap than silicon conventionally widely used as a material for forming a semiconductor device. Therefore, by adopting silicon carbide as a material for forming a semiconductor device, a higher breakdown voltage, a lower ON resistance of a semiconductor device and the like can be achieved. In addition, a semiconductor device adopting silicon carbide as a material is also more advantageous than a semiconductor device adopting silicon as a material in that deterioration in its characteristics at the time when it is used in an environment at high temperature is less.
A semiconductor device including silicon carbide as a material is manufactured, for example, by forming an epitaxial growth layer on a silicon carbide substrate, fabricating a region in the epitaxial growth layer, in which a desired impurity has been introduced, and forming an electrode. The silicon carbide substrate is generally manufactured by cutting (slicing) a crystal (an ingot) of silicon carbide. Silicon carbide, however, has extremely high hardness and hence cutting thereof is not easy. Therefore, a method of cutting silicon carbide crystal has variously been studied and various methods have been proposed (see, for example, Japanese Patent Laying-Open No. 2009-61528 (PTL 1)).
With a conventional method of cutting a silicon carbide crystal, however, warpage of an obtained substrate is disadvantageously great. Warpage of a substrate can be lessened by polishing or the like after cutting. If a substrate great in warpage is planarized by polishing or the like, however, a plane orientation of silicon carbide single crystal in a main surface of the substrate varies from place to place. Silicon carbide single crystal has different characteristics depending on a plane orientation of a crystal. Therefore, preferably, warpage is lessened in the stage of cutting a substrate such that variation in plane orientation above in the main surface of the substrate is suppressed.